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Quieter Pavement Performance in Washington State. University of Washington a nd the Washington State Department of Transportation. Rocky Mountain Asphalt Conference Denver, CO January 19, 2009. Topics. Noise basics What are quieter pavements? State experience
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Quieter Pavement Performance in Washington State University of Washington and the Washington State Department of Transportation Rocky Mountain Asphalt Conference Denver, CO January 19, 2009
Topics • Noise basics • What are quieter pavements? • State experience • Arizona pavements in Phoenix • Washington State experience • Interstate 5 • SR 520 • Bottom Line
Sound Pressure Scales Source: EPD, Hong Kong
Noise Basics Source: ”Fundamentals and Abatement of Highway Traffic Noise” FHWA, June 1973. Sound level change of 1 dB can barely be detected by humans Change of 2 to 3 dB, barely noticeable. Change of 5 dB, readily noticeable. Change of 10 dB perceived as a doubling in loudness. Change of 20 dB represents a dramatic change. Change of 40 dB represents the difference between a faintly audible sound and a very load sound.
Noise Basics • The minimum change in sound level that a human ear can detect is about 3 dB. • The average person perceives a change in sound level of about 10 dB as a doubling or halving the sound’s loudness • The table to the left shows a relationship between dBA and “noise loudness” levels. • 70 to 80 dB: 2x as loud • 70 to 90 dB: 4x as loud • 70 to 100 dB: 8x as loud etc. • Source: Table 1 from a noise analysis report entitled “Tijuana River Valley Regional Park, Trails and Habitat Enhancement Project,” San Diego Dept of Public Works, Prepared by Kimley-Horn and Associates, Inc. July 2005
Quieter pavements initially reduce the noise created as a tire rolls along the pavement surface Noise reduction results from surface texture Finer gradation quieter the pavement Aggregate size < 3/8 inch Need 15-20 percent air voids Europeans find a two layer concept with ¾ inches of fine graded OGFC over 1-½ inches of coarse graded OGFC provides best noise reduction What are Quieter HMA Pavements
1” Asphalt Pavement - Surface Texture Open-graded friction course Dense-graded Hot Mix Asphalt
Performance of WSDOT Class D Mixes is strongly affected by studded tire wear
Asphalt rubber Incorporates recycled tires (tread only) Improves durability (aging) properties of the asphalt binder Contributes ~1 dB(A) noise reduction Polymer modified Rubber (not recycled tire) product Styrene-butadiene-styrene (SBS) Improves durability (aging) properties of the asphalt binder Contribution to noise reduction, if any, is unknown Asphalt Binder Types
What are Typical Sound Levels? On-Board Sound Intensity (dBA) OBSI Device
Southern states (AZ, CA, FL, GA, NC, SC and TX) indicate average life of 10 to 12 years Placement temperature AZDOT requires 85ºF surface temperature CALTRANS allows 60ºF air temperature Contractor (Granite Construction) prefers 70ºF air temperature Challenge was placement during night time construction in western WA (contract allowed 55ºF air temperature) Experience of other states
Arizona Performance I-17 118,000 ADT 8 to 9 years old Photo courtesy of Joe Mahoney
Arizona Performance Photo courtesy of Joe Mahoney Photo courtesy of Joe Mahoney
Arizona first used asphalt rubber products in 1964 (City of Phoenix). Early ADOT use was for a chip seal in 1968, Placed first non-experimental section of ARFC in 1985 on I-17. Current ARFC consists of: 3/8” minus open graded aggregate Asphalt rubber binder with a content ranging between 9.0 to 9.6% by weight of total mix. Used to overlay PCC since 1988. Asphalt Rubber Friction Course (ARFC)
I-17 ARFC 1” surfacing, MP 199, age ~ 4 years(original PCC slabs constructed in 1960 9” thick and overlayed in 1990 with ARFC—at that time slabs were faulting and needed joint patching—this is the second ARFC overlay at this location) Northbound view—ARFC in good condition.
US 60 Eastbound, ARFC 1” surfacing, approximately MP 175-178, age ~ 5 to 6 years
US 60 Eastbound, ARFC 1” surfacing, approximately MP 175-178, age ~ 5 to 6 years PCC approximately 11 to 13 inches thick. Note ARFC and transverse tined PCC.
Studded tires No to minimal use in southern states Is a major issue in Washington State Prior Class D experience (earlier open graded) Washington State Experience
Test Project Details and Results(Lynnwood, WA) • South bound only • OGFC-AR • OGFC-SBS • ½” Dense-graded HMA HOV Lane 3 Lane 2 Lane 1
Interstate 5Open graded—rubber asphalt binder Wear or Rut Depth (mm) Smoothness (IRI) Sept 2006 Jan 2009 Sound Intensity (dBA)
Interstate 5Open graded—SBS binder Wear or Rut Depth (mm) Smoothness (IRI) Sept 2006 Jan 2009 Sound Intensity (dBA)
Interstate 5HMA Control Section Smoothness Wear or Rut Depth Apr 2007 Sound Intensity (dBA) Jan 2009
Test Project Details and Results (SR-520 near Bellevue) • Both directions • OGFC-AR • OGFC-SBS • ½” dense-graded HMA HOV Lane 3 Lane 2 Lane 1
Late breaking news… • The open graded sections on I-5 and SR 520 were damaged by tire chains and studs during the heavy snows of December 2008.
SR 520 open graded mix damage HMA section—Jan 2009 OGFC-AR—Jan 2009
Bottom Line • Open graded surfacings have converged on dense graded HMA with respect to measured sound levels. Snow during December 2008 accelerated the convergence. • Improved binders have not solved the studded/chained tire problem. • Reduced noise levels were destroyed by buses with tire chains. • Personal conclusion: The current family of open graded surfacings do not work in a studded/chained tire environment.
Questions? Photo courtesy S. Muench